Optical disc recording apparatus and method, and computer program

ABSTRACT

An information recording apparatus ( 1 ) is provided with: a recording device ( 102 ) for recording information onto an information recording medium ( 100 ) by irradiating the information recording medium with a recording laser beam (L); a controlling device ( 103 ) for recording calibration data onto the information recording medium by using the recording laser beam in which the power is adjusted gradually; and a detecting device ( 107 ) for detecting degree of modulation of a reproduction signal after the recording of the calibration data, the recording of the calibration data being ended if the degree of modulation exceeds a predetermined range, an optimum power of the recording laser beam being determined from a jitter amount included in a reproduction signal.

TECHNICAL FIELD

The present invention relates to an information recording apparatus andmethod, such as a DVD recorder, and a computer program which makes acomputer function as the information recording apparatus.

BACKGROUND ART

In an information recording/reproducing apparatus for recording dataonto an information recording medium, for example, such as an opticaldisc, the optimum power of a recording power is set by an OPC (OptimumPower Control) process in accordance with the type of the optical disc,the type of the recording apparatus, a recording speed, or the like. Inother words, the recording power is calibrated. This can realize anappropriate recording operation in response to variations in property ofthe information recording surface of the optical disc, or the like. Forexample, when the optical disc is loaded and a writing command isinputted, the light intensity of a recording laser beam is changedsequentially and gradually, and OPC data is recorded into an OPC area;namely, a so-called test-writing process is performed. After that, theOPC data recorded in this manner is reproduced, and this reproductionresult is judged by a predetermined evaluation criterion to obtain thecalibration value (e.g. optimum recording power) of the recording power.

Moreover, the OPC that is simultaneously performed with the actualrecording operation (i.e. running OPC) also allows the setting of theoptimum recording power associated with the recording laser beam.

-   Patent document 1: Japanese Patent No. 3159454

DISCLOSURE OF INVENTION Subject to be Solved by the Invention

However, the upper limit value of the recording power which changes is afixed value in the calibration process, so that the recording isperformed with an excessive recording power that exceeds the detectablelimit of a push-pull signal in some recording media to be used, and thismay interfere with a system operation, which is technically problematic.Moreover, in an apparatus of such a type that the recording is startedwith a relatively large recording power as an initial value and that thecalibration is performed with the recording power reduced sequentially,not only the upper limit value of the recording power but also therecording power as the initial value likely exceed the detectable limitof the push-pull signal in the first place.

In view of the aforementioned problems, it is therefore an object of thepresent invention to provide an information recording apparatus andmethod which can preferably determine the optimum power when the data isrecorded onto the information recording medium, such as an optical disc,and a computer program which makes a computer function as theinformation recording apparatus.

Means for Solving the Subject

The above object of the present invention can be achieved by aninformation recording apparatus provided with: a recording device forrecording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling device for controlling therecording device to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting device for detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling device; an ending device for endingthe irradiation of the recording laser beam by the control of thecontrolling device in a case where the degree of modulation detected bythe detecting device exceeds a predetermined range; and a determiningdevice for determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending device.

The above object of the present invention can be also achieved by aninformation recording method provided with: a recording process ofrecording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling process of controlling therecording process to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting process of detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling process; an ending process of endingthe irradiation of the recording laser beam by the control of thecontrolling process in a case where the degree of modulation detected bythe detecting process exceeds a predetermined range; and a determiningprocess of determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending process.

The above object of the present invention can be also achieved by acomputer program for making a computer function as: a recording devicefor recording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling device for controlling therecording device to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting device for detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling device; an ending device for endingthe irradiation of the recording laser beam by the control of thecontrolling device in a case where the degree of modulation detected bythe detecting device exceeds a predetermined range; and a determiningdevice for determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram conceptually showing the basic structure of anexample of the information recording apparatus of the present invention.

FIG. 2 is a flowchart conceptually showing an overall flow of anoperation example of the recording apparatus of the present invention.

FIG. 3 is a block diagram conceptually showing the basic structure in acircuit example of a modulation degree detection circuit in therecording apparatus of the present invention.

FIG. 4 is a graph example showing a relation between a recording powerand degree of modulation in the circuit example of the modulation degreedetection circuit in the recording apparatus of the present invention.

FIG. 5 is a conceptual view showing the structure of a data recordingarea for judging that calibration data is recorded onto an informationrecording medium in the example of the information recording apparatusof the present invention.

DESCRIPTION OF REFERENCE CODES

-   101 spindle motor-   102 optical pickup-   103 control device-   104 memory-   105 information recording device-   106 signal adjustment device-   107 modulation degree detection device-   108 information reproducing device-   109 recording quality judgment device-   201 modulation degree detection circuit-   202 modulation degree memory-   203 comparison circuit-   204 reproduction signal-   205 degree of modulation-   206 previous degree of modulation-   207 memory update timing-   301 OPC area-   302 a, b unit OPC area-   303 calibration area-   304 a, b determination area

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, as the best mode for carrying out the present invention, anexplanation will be given on an information recording apparatus andmethod, and a computer program in embodiments of the present invention.

An embodiment of the information recording apparatus of the presentinvention is an information recording apparatus provided with: arecording device for recording information onto an information recordingmedium by irradiating the information recording medium with a recordinglaser beam whose power can be adjusted; a controlling device forcontrolling the recording device to record calibration data byirradiating the information recording medium with the recording laserbeam in which the power is adjusted gradually; a detecting device fordetecting degree of modulation in an area in which the calibration datais recorded on the information recording medium every time the power isadjusted gradually by the control of the controlling device; an endingdevice for ending the irradiation of the recording laser beam by thecontrol of the controlling device in a case where the degree ofmodulation detected by the detecting device exceeds a predeterminedrange; and a determining device for determining an optimum power forrecording the information, on the basis of a reproduction signalobtained by reading the calibration data after the irradiation of therecording laser beam is ended by the control of the ending device.

According to the embodiment of the information recording apparatus ofthe present invention, it is possible to record various contentinformation including video information, music information, datainformation for computer, and the like.

Particularly in the embodiment, when the information recording apparatusirradiates the information recording medium with the recording laserbeam to record the information, the controlling device records thecalibration data by irradiating the information recording medium withthe recording laser beam in which the power is adjusted gradually.Moreover, in the case where the degree of modulation detected by thedetecting device exceeds the predetermined range, the ending device endsthe irradiation of the recording laser beam for recording thecalibration data by the controlling device. Then, on the basis of therecording quality, such as a jitter and degree of modulation, obtainedfrom the reproduction signal detected by the irradiation of a readinglaser beam (in other words, a reading signal obtained by reading therecorded calibration data), the determining device determines theoptimum power of the laser beam when the information is recorded.

Here, the “calibration data” indicates test-writing data (e.g. OPC dataor the like) recorded to determine the optimum power for recording theinformation. Moreover, the “optimum power” indicates the power of therecording laser beam that is most appropriate or almost appropriate forthe recording of the information.

As a result, according to the embodiment of the information recordingapparatus of the present invention, when the optimum power of therecording laser beam is determined (specifically, for example, in theOPC), the reproduction signal is detected by applying the reading laserbeam after applying the recording laser beam, and the optimum power isdetermined on the basis of the detection result. In particular, in orderto control the ending device to end the recording of the calibrationdata if the degree of modulation exceeds the predetermined range whenthe calibration data is recorded with the power of the recording laserbeam changed gradually, as detailed later, it is possible to end therecording of the calibration data before the push-pull signal of therecorded calibration data reaches to an inappropriate level. Thus,without placing an unnecessary burden on the recording apparatus byperforming the recording with an inappropriate power, or by omitting theprocess, the optimum power can be determined, safely and quickly. As aresult, the information can be recorded with a more preferable power,and for example, a recording error and a reproduction error in thereproduction of the information can be reduced.

In one aspect of the embodiment, the case where the degree of modulationdetected by the detecting device exceeds the predetermined range is acase where a push-pull signal estimated from the degree of modulationdetected by the detecting device exceeds a reading limit level of thepush-pull signal.

Here, the “push-pull signal” is a signal indicates the difference in theoutputs from the respective divided detectors when the reading laserbeam is irradiated to the information recording medium such as anoptical disc, and the reproducing signal obtained from the returnedlight which is reflected and diffracted is detected by the divideddetectors. By detecting the push-pull signal, tracking control or thelike can be performed, and as a result, the information recorded on theinformation recording medium can be read. The intensity level of thepush-pull signal is the highest in an unrecorded state, and it isreduced by recording the data. The reading limit level of the push-pullsignal indicates the intensity level of the push-pull signal in whichincreasing the recording power causes a too small push-pull signal (i.e.too much difference from the amplitude of the push-pull signal in theunrecorded area), thereby making the tracking control unstable and thusmaking it hard or impossible to read the information recorded on theinformation recording medium.

Moreover, the degree of modulation is determined by the reflectance ofthe information recording medium, the power of the recording laser beamto be irradiated, and the like. The degree of modulation about the datarecorded on one optical disc increases with an increase in the power ofthe recording laser beam. In other words, there is a mutual relationbetween the value of the degree of modulation and the intensity level ofthe push-pull signal, on the one optical disc. Here, if the readinglimit level of the push-pull signal corresponding to the optical disc tobe recorded on in advance, the calibration data can be recorded, withthe power of the recording laser power changed in the range in which therecorded data can be read, by confirming the degree of modulation.

As a result, when the calibration data is recorded onto the informationrecording medium in this aspect, the calibration data can be recorded atthe level that the push-pull signal does not interfere with theoperation of the information recording apparatus.

In one aspect of the embodiment, the information recording medium allowsreflectance to be increased when the information is recorded.

According to this aspect, in the information recording medium in theembodiment, the reflectance is increased by recording the information,and the amount of the returned light which is reflected with respect tothe amount of the recording laser beam irradiated is increased.

Moreover, as an aspect of this information recording apparatus, thecontrolling device may control the recording device to record thecalibration data by using the recording laser beam with one power andthen record the calibration data by using the recording laser beam withanother power, which is greater than or equal to the one power, when thepower is adjusted gradually.

By virtue of such construction, by adjusting the amount of the recordinglaser beam from the low power side, it is possible to detect the limitlevel of the degree of modulation corresponding to the reading limitlevel of the push-pull signal in the adjustment process. As a result, itis possible to avoid such a situation that a failure in the detection ofthe push-pull signal interferes with a tracking operation due to theirradiation with a high power which exceeds the reading limit level ofthe push-pull signal from the beginning.

Moreover, by ending the recording of the calibration data at the time ofdetecting that the degree of modulation reaches to the limit level, itis unnecessary to record the calibration data in an unnecessary powerrange which is inappropriate for the recording of the information. Thus,it is possible to shorten the process of recording the calibration datafor determining the optimum power.

Moreover, the controlling device may end the recording of thecalibration data and then irradiate again an area on the informationrecording medium that is adjacent to an area in which the calibrationdata is recorded, with a power that is less than or equal to a powerimmediately before the recording of the calibration data is ended.

By virtue of such construction, it is possible to make a data recordingarea for judging that the calibration data is recorded in the area thatis adjacent to the area in which the calibration data is recorded, andthis facilitates the detection of an area in which the calibration datahas not been recorded yet. In particular, if the calibration data isrecorded to increase the power sequentially, it is likely hard todistinguish between the area with the calibration data recorded and thearea that is adjacent to the aforementioned area and in which thecalibration data has not been recorded yet, because the calibration datais recorded with the lowest power at the beginning. Thus, it is possibleto clearly identify the edge of the area in which the calibration datais recorded, by performing the recording to be adjacent to the area inwhich the calibration data is recorded at the beginning, with the powerthat is less than or equal to the power immediately before the recordingof the calibration data is ended (i.e. the highest power). The recordingof the data for identifying the area with the calibration data recordedmay be performed with a power that is less than or equal to the powerwhen the calibration data is recorded last time and that can realize adetectable amplitude. Moreover, the recording may be performed not onlywith the same power but also with a plurality of powers.

In another aspect of the embodiment, the information recording apparatusis further provided with: a judging device for judging whether or notrecording quality of the information recorded by using the recordinglaser beam with the optimum power determined by the determining deviceis at an acceptable level; and a modifying device for adjusting arecording pulse of the recording laser beam if it is judged that therecording quality is not at the acceptable level.

According to this aspect, when the information is recorded with thedetermined optimum power of the recording laser beam, if the recordingquality of the information is not at the acceptable level, then, therecording quality of the information is corrected by adjusting therecording pulse.

Here, “adjusting the recording pulse” is adjusting either or both of thepulse width and pulse intensity of the pulse in the recording of theinformation including a pulse train. When the information is recorded byusing the recording laser beam, the shape of a pit on the informationrecording medium formed by the irradiation of the recording laser beamis influenced not only by the power of the recording laser beam but alsoby the reflectance and sensitivity of the information recording medium.In the embodiment, the recording quality can be kept preferable byadjusting the recording pulse after the determination of the optimumpower of the recording laser beam.

Alternatively, in an aspect in which the information recording apparatusis provided with the modifying device, the controlling device controlsthe recording device to record the calibration data again after theadjustment of the recording pulse of the recording laser beam on themodifying device.

By virtue of such construction, even if the optimum power in theinformation recording is changed by adjusting the recording pulse of therecording laser beam, it is possible to determine the optimum powerafter the change by recording the calibration data again.

In another aspect of the embodiment, the detecting device detects adifference between the degree of modulation in each power of thegradually adjusted recording power and the degree of modulation in aprevious recording power of the gradually adjusted recording power whendetecting the degree of modulation.

According to this aspect, the detecting device calculates and detectsthe difference between the degree of modulation in each recording powergradually adjusted and the degree of modulation in the previousrecording power. As the recording power increases, the degree ofmodulation also increases; however, a rate of increase in the degree ofmodulation gradually decreases. In other words, in the relatively largerecording power, a change in the degree of modulation with respect tothe recording power is small, and when the value of the degree ofmodulation itself is seen, it is hard and mostly pointless to judgewhether or not it reaches to a predetermined value. On the other hand,by checking the difference between the degree of modulation in oneparticular recording power and the degree of modulation in the previousrecording power, it is possible to check the change in the degree ofmodulation with respect to the recording power. By virtue of theaforementioned construction, by checking whether or not the change inthe degree of modulation reaches to the predetermined value there issuch a remarkable effect that the state of the degree of modulationcorresponding to the recording power can be seen in a more sensitivemanner.

An embodiment of the information recording method of the presentinvention is an information recording method provided with: a recordingprocess of recording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling process of controlling therecording process to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting process of detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling process; an ending process of endingthe irradiation of the recording laser beam by the control of thecontrolling process in a case where the degree of modulation detected bythe detecting process exceeds a predetermined range; and a determiningprocess of determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending process.

According to the embodiment of the information recording method of thepresent invention, it is possible to receive the same various effects asthose of the aforementioned embodiment of the information recordingapparatus of the present invention.

Incidentally, the embodiment of the information recording method of thepresent invention can also adopt the same various aspects in theembodiment of the information recording apparatus of the presentinvention described above.

An embodiment of the computer program of the present invention is acomputer program for making a computer function as: a recording devicefor recording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling device for controlling therecording device to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting device for detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling device; an ending device for endingthe irradiation of the recording laser beam by the control of thecontrolling device in a case where the degree of modulation detected bythe detecting device exceeds a predetermined range; and a determiningdevice for determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending device.

According to the computer program of the present invention, theaforementioned embodiment of the information recording apparatus of thepresent invention can be relatively easily realized as a computerprovided in the motion picture editing apparatus reads and executes thecomputer program from a program storage device, such as a ROM, a CD-ROM,a DVD-ROM, and a hard disk, or as it executes the computer program afterdownloading the program through a communication device.

Incidentally, in response to the various aspects in the embodiment ofthe information recording apparatus of the present invention describedabove, the embodiment of the computer program of the present inventioncan also adopt various aspects.

The operation and other advantages in the embodiment will become moreapparent from the example explained below.

As explained above, according to the embodiment of the informationrecording apparatus of the present invention, it is provided with therecording device, the controlling device, the detecting device, theending device, and the determining device. According to the embodimentof the recording method of the present invention, it is provided withthe recording process, the controlling process, the detecting process,the ending process, and the determining process. According to theembodiment of the computer program of the present invention, it makes acomputer function as the recording device, the controlling device, thedetecting device, the ending device, and the determining device.Therefore, it is possible to provide an information recording apparatusand method which can preferably determine the optimum power when thedata is recorded onto the information recording medium, such as anoptical disc, and a computer program which makes a computer function asthe information recording apparatus.

EXAMPLE Structure Example

The structure example of the information recording apparatus in anexample of the present invention will be explained with reference toFIG. 1. Incidentally, the same constituent elements in the drawings willcarry the same referential numerals. FIG. 1 is a block diagramconceptually showing the basic structure of an example of theinformation recording apparatus of the present invention.

As shown in FIG. 1, an information recording apparatus 1 in the exampleis provided with a spindle motor 101, an optical pickup 102, a controldevice 103, a memory 104, an information recording device 105, a signaladjustment device 106, a modulation degree detection device 107, aninformation reproducing device 108, and a recording quality judgmentdevice 109.

The optical pickup 102 is one specific example of the “recording device”of the present invention. The optical pickup 102 is provided with asemiconductor lens apparatus, various lenses, an actuator, and the like.More specifically, the optical pickup 102 irradiates an optical disc 100with a laser beam L as reading light with a first power in reproduction.An obtained reproduction signal is passed to the information reproducingdevice 108 to reproduce the data. On the other hand, the optical pickup102 irradiates the optical disc 100 with the laser beam L as writinglight with a second power and with it modulated in recording. The poweradjustment of the laser beam L is performed under the control of thesignal adjustment device 106 which is one example of the “controllingdevice” described later. More specifically, the irradiation is performedwith the laser beam L with a predetermined power by driving thesemiconductor laser apparatus by a driving pulse defined by apredetermined pulse strategy.

The spindle motor 101 is constructed to rotate the optical disc 100 at apredetermined speed, under spindle servo provided by a not-illustratedservo circuit or the like. Moreover, the optical disc 102 is constructedto be displaced in the radial direction of the optical disc 100 or thelike by the not-illustrated servo circuit or the like. As a result,various data can be recorded by applying the laser beam L at a desiredrecording position on the optical disc 100.

The signal recording device 105 is one example of the “controllingdevice” in the structure example of the present invention. The signalrecording device 105 drives the semiconductor laser disposed in theoptical pickup 102 in order to detect the optimum power of the laserbeam by processes of recording and reproducing an OPC pattern describedlater, in an OPC process described later. After that, in the datarecording, the signal recording device 105 is constructed to drive thesemiconductor laser of the optical pickup 102 with the optimum powerdetected by the OPC process. In the data recording, the optimum power ismodulated in accordance with record data.

The signal adjustment device 106 is constructed to output a signalindicating the OPC pattern to the information recording device 105 inthe recording of the OPC pattern in the OPC process before a recordingoperation described later. The information recording device 105 passesthe recording signal indicating the OPC pattern, to the optical pickup102, by which the calibration data is recorded.

After the recording of the calibration data, the optical pickup 102irradiates the optical disc 100 with a reading laser beam L, thereturned light which is reflected and diffracted is passed to themodulation degree detection device 107, and the value of the degree ofmodulation is detected from the reproduction signal obtained from thereturned light. Moreover, the optimum amount of light for data recordingis determined from a jitter amount or the like included in thereproduction signal obtained from the returned light.

After the recording of the calibration data, the data recorded by usingthe laser beam L with the optimum power is reproduced. The recordingquality judgment device 109 judges whether or not the recording qualityof the reproduction signal passed to the information reproducing device108 is at an acceptable level. If it is judged to be less than or equalto the acceptable level, the pulse strategy of the record data isadjusted on the signal adjustment device 106.

Incidentally, in the information recording apparatus 1 shown in FIG, 1,in order to give a simpler explanation on the characteristics of theexample of the present invention, constituent features required for thestructure example are extracted and illustrated. Thus, it is acceptableto provide the constituent features other than the aforementionedconstituents.

Operation Example

Next, with reference to a flowchart in FIG. 2, an explanation will begiven on the details of the OPC process of the information recordingapparatus as constructed above.

When the optical disc 100 is loaded on the spindle motor 101, a seekoperation is performed by the optical pickup 102 under the control ofthe control device 103, thereby obtaining various management datanecessary for the recording process to be performed on the optical disc100. On the basis of the management data, the data is recorded onto theoptical disc 100 through the information recording device 105 inaccordance with an instruction from external input equipment or thelike, by the control of the control device 103. Then, the OPC process isperformed as the calibration of the recording laser power before therecording of the data.

Firstly, identification is performed about whether or not the opticaldisc 100 loaded on the spindle motor 101 is a known disc (step S101).Here, the “known disc” indicates a disc in which the degree ofmodulation of the reproduction signal obtained when the disc isirradiated with the reading laser beam with one particular power. Thedegree of modulation of the reproduction signal obtained from thereturned light includes an error depending on a state on the opticaldisc 100. In order to detect the degree of modulation accurately, it isnecessary to identify the degree of modulation of the reproductionsignal in the optical disc 100. Moreover, the degree of modulation inthe same optical disc 100 is uniquely determined by the power of therecording laser beam L when the data is recorded, so it is associatedwith the amplitude of a push-pull signal uniquely determined likewise.Hence, if the acceptable limit value of the amplitude of the push-pullsignal is determined which allows the record data to be read, theacceptable limit value of the degree of modulation corresponding to theacceptable limit value of the amplitude of the push-pull signal is alsodetermined.

The identification method of the optical disc 100 includes, for example,a method of reading identification information recorded in apredetermined area on the optical disc 100, a method of irradiating theoptical disc 100 with the laser beam L, detecting the reproductionsignal corresponding to the returned light, and identifying the degreeof modulation of the optical disc 100 on the basis of the reproductionsignal obtained, and the like.

If the optical disc 100 is the known disc (the step S102: Yes), theacceptable limit value of the degree of modulation corresponding to thedisc is read from the memory 104 and is set (step S103).

Moreover, if the optical disc 100 is not the known disc (e.g. if theoptical disc 100 is a disc in which information associated with thereflectance of the disc is not identified) (the step S102: No), theacceptable limit value of the degree of modulation is newly set or theacceptable limit value of the degree of modulation of default is set,from the information obtained in the disc identification (the step S101)(step S104). Moreover, the identification information associated withthe disc is recorded into the memory 104 at least in association withinformation about the acceptable limit value of the degree of modulationassociated with the disc. Then, if the disc 100 having the sameidentification information is detected, the acceptable limit value ofthe degree of modulation recorded is read and set (the step S103).

Then, one particular power of the laser beam L for recording thecalibration data is set by the signal adjustment device 106 (step S105).

Incidentally, in the example, it is assumed that the optical disc 100 inwhich the reflectance is increased by recording the data (i.e. byapplying the laser beam L) (so-called L to H media) is used. In thiscase, the one particular power of the laser beam L set in the step S105is the power of the laser beam L to the extent that does not exceed theamplitude limit value of the push-pull signal which allows the recordedinformation to be read and a relatively low power. Moreover, as detailedlater, the calibration data is recorded with the power of the laser beamL increased sequentially, in the OPC process.

However, obviously, it may be constructed such that the optical disc 100in which the reflectance is reduced by recording the data (i.e. byapplying the laser beam L) is used. In other words, it is a case wherethe power of the laser beam L set in the step S105 is the power of thelaser beam L to the extent that does not exceed the amplitude limitvalue of the push-pull signal which allows the recorded information tobe read and a relatively high power. Moreover, in this case, thecalibration data is recorded with the power of the laser beam L reducedsequentially, in the OPC process.

Then, the one particular power of the laser beam L is passed to theinformation recording device 105, and under the control of theinformation recording device 105, the calibration data is recorded ontothe optical disc 100 with the one particular power (step S106).

If the recording of the calibration data with the one particular powerin a predetermined area is ended, then, the degree of modulation of thereproduction signal in the area is obtained (step S107). The modulationdegree detection device 107 calculates a difference in values betweenthe obtained degree of modulation and the degree of modulation of thereproduction signal in an area recorded with a previous recording power,which is read from a modulation degree memory 202 in FIG. 3 detailedlater. Moreover, the value of the degree of modulation is stored in themodulation degree memory 202 until a difference from at least nextdegree of modulation is calculated (refer to FIG. 4).

Then, it is judged whether or not the calculated difference value of thedegree of modulation exceeds the acceptable limit value of the degree ofmodulation which is set (step S108).

If the degree of modulation does not exceed the acceptable limit value(the step S108: No), the control device 103 is notified of the result bythe modulation degree detection device 107, and the informationrecording device 105 increases the power of the recording laser beam Lunder the control of the control device 103 which is notified of theresult (step S109). When the power of the recording laser beam L isincreased, a predetermined amount may be used for the increase amount inone operation. After the power of the laser beam L is increased, therecording of the calibration data is performed again with the power(step S106).

On the other hand, if the degree of modulation does not exceed theacceptable limit value (the step S108: Yes), the control device 103 isnotified of the result by the modulation degree detection device 107,and the information recording device 105 ends the recording of thecalibration data under the control of the control device 103 (stepS110). According to this operation, when or before it becomes hard orimpossible to read the information recorded on the optical disc 100 dueto a too small push-pull signal, the recording of the calibration datacan be ended. As a result, it is possible to achieve such a markedeffect that the calibration data can be stably recorded by notperforming the recording in an area which allows an excess of thereading limit level of the push-pull signal.

After the end of the recording, the power of the laser beam L used in anarea which provides the smallest jitter amount in the reproductionsignal in an area on the optical disc 100 in which the calibration datais recorded by adjusting the power gradually is determined as theoptimum power (step S111). Specifically, the optimum power is determinedby detecting the jitter amount from the reproduction signal obtained byirradiating the area in which the calibration data is recorded, with thereading laser beam L. The process of detecting the jitter amount may beperformed on the entire area after the recording of the calibration datais ended. Alternatively, in the process of detecting the push-pullamplitude in each power, the jitter amounts in the powers may bedetected simultaneously, stored in the memory 104, and compared later.For example, an error rate, degree of modulation, or asymmetry may beused as an index, instead of the jitter amount.

It may be or may not be also constructed such that the recordingcompensation process in which the pulse strategy of the data forrecording is adjusted to achieve the appropriate recording quality isperformed after the optimum power is determined. In the recordingcompensation process, firstly, the data is recorded by using the laserbeam L with the optimum power, and at the same time, the recorded datareproduced, and the reproduction signal is passed to the informationreproducing device 108 (step S112). Then, it is judged on the recordingquality judgment device 109 whether or not the recording quality of thedata is at the acceptable level (step S113). If the judgment result doesnot achieve the acceptable level of the recording quality (the stepS113: No), the correction of the pulse strategy (e.g. the correction ofat least one of the pulse width and the amplitude of the pulse strategy)is performed on the signal adjustment device 106 (step S114).Incidentally, if a change in the amplitude of the pulse strategy changesthe power of the laser beam L, resulting in a change in the condition ofthe optimum power (step S115: Yes), then, the calibration data isrecorded again (the step S106), and the optimum power is obtained again.

According to this operation, the pulse strategy of the data forrecording is corrected on the basis of the determination of a pit shapeformed by actually recording the data or the like, so that it ispossible to keep the optimum recording quality of the data. Moreover, ifthe condition for determining the optimum power is changed due to thecorrection of the pulse strategy, then, the pulse strategy after thecorrection is used to obtain the optimum power again, by which themarked effect which keeps the preferable recording quality can beobtained.

If the recording quality of the data is within the acceptable level (thestep S113: Yes), or if there is no need to obtain the optimum poweragain after the correction of the pulse strategy (the step S115: No),the determined optimum power and pulse strategy are stored into thememory 104, and the data is recorded on the basis of the optimum powerand the pulse strategy under the control of the control device 103.

Examples of Modulation Degree Detection Circuit

Next, with reference to FIG. 3 and FIG. 4, an explanation will be givenon the details of the detection of the degree of modulation in theexample (i.e. the modulation degree detection device 107). FIG. 3 showsthe example of the modulation degree detection device 107 in theexample, wherein FIG. 3 is a block diagram showing the basic structureof a circuit for detecting the difference value between the degree ofmodulation in a particular recording power and the degree of modulationin a previous recording power. FIG. 4 is a graph example showing arelation among the degree of modulation of the reproduction signaldetected in an OPC area, the difference value between the degree ofmodulation in the particular recording power and the degree ofmodulation in the previous recording power, the amplitude of thepush-pull signal detected in the OPC area, and the jitter amountincluded in the reproduction signal detected in the OPC area.

The modulation degree detection circuit 107 in the circuit example shownin FIG. 3 is provided with a modulation degree detection circuit 201, amodulation degree memory 202, and a comparison circuit 203.

By the control of the optical pickup 102 in FIG. 1, a reproductionsignal 204 is inputted to the modulation degree detection device 107when the calibration data recorded on the optical disc 100 is read.

Then, on the modulation degree detection circuit 201, the degree ofmodulation of the reproduction signal 204 is detected and sent to thecomparison circuit 203. A previous degree of modulation 206 detectedfrom the reproduction signal in the OPC area recorded with the previousrecording power is also sent from the modulation degree memory 202 tothe comparison circuit 203. Moreover, in response to an instruction ofmodulation degree memory update timing 207 from the control device 103,a degree of modulation 205 sent from the modulation degree detectioncircuit 201 is stored into the modulation degree memory 202, and theprevious degree of modulation 206 is updated.

On the comparison circuit 203, a difference between the degree ofmodulation 205 and the previous degree of modulation 206 is calculatedand outputted to the control device 103. Then, on the control device103, it is judged whether or not the difference exceeds the acceptablelimit value of the degree of modulation.

With reference to the graph example shown in FIG. 4, an explanation willbe given on the method of estimating the push-pull signal level usingthe degree of modulation of the reproduction signal. The upper part ofthe graph shows the degree of modulation 205 of the reproduction signalwith respect to the recording power of the recording laser beam L, thedifference value between the degree of modulation 205 and the previousdegree of modulation 206, the amplitude of the push-pull signal detectedin the OPC area, and the jitter amount included in the reproductionsignal detected in the OPC area (i.e. a shift amount in a time axisdirection of the recording pulse). As shown in FIG. 4, as the powerincreases, the degree of modulation 205 increases, but its increaseamount decreases as shown by the difference in degree of modulation, andthe value of the push-pull amplitude also decreases.

An operation of calibrating the power by the OPC using this circuitexample will be explained. Firstly, in the calibration of the power bythe OPC, starting from a power low enough to obtain the push-pull signallevel which is at least greater than or equal to a detectable limitvalue, the recording of the calibration data with one particular poweris performed, and then, the degree of modulation of the reproductionsignal in the area in which the calibration data is recorded isdetected, as shown in the lower part of FIG. 4. In the recording anddetecting processes, the recording is performed with the recording powerincreased sequentially and gradually, until the difference value betweenthe degree of modulation and the previous degree of modulation in theprevious recording power exceeds the acceptable limit value of thedegree of modulation (the step S103 to the step S106 in FIG. 2). Theprocess of recording the calibration data is ended when the detecteddifference value of the degree of modulation exceeds the acceptablelimit value of the degree of modulation (the step S107 in FIG. 2).

Then, in the area in which the calibration data is recorded, a valuewhich provides the smallest jitter amount is determined as the optimumpower (the step S108 in FIG. 2). According to this operation, it ispossible to determine the optimum power which provides the smallestjitter amount while recording the calibration data in the range thatdoes not exceed the detection limit of the push-pull signal level.

Example of Judgment of Calibration Area

By using FIG. 5, an explanation will be given on an operation of forminga data recording area for judging that the calibration data is recordedon the information recording medium. FIG. 5 is a conceptual view showingan information recording area when the calibration data is recorded ontoan OPC area 301 on the optical disc 100. As shown in FIG. 5, an OPC area302 in which the calibration data is recorded on the optical disc 100 isprovided with a calibration area 303 in which the calibration data isrecorded; and a judgment area 304 which is adjacent to the area with thecalibration data recorded and in which judgment data is recorded,wherein the judgment data indicates that the calibration data isrecorded (in other words, the judgment data indicates a boundary betweenthe area with the calibration data recorded and an area with nocalibration data recorded).

Next, an explanation will be given on the operation of recording thecalibration data and the judgment data. Firstly, in the OPC area 301 ofthe optical disc 100 shown in FIG. 5, an unused area in which the datais not recorded is sought from a front edge in a spiral direction(hereinafter simply referred to as the front edge) to a rear edge. If nodata is recorded on the OPC area 301, i.e. if the OPC is performed forthe first time, the rearmost edge of the OPC area 301 is sought.

The recording of the calibration data into the sought unused area isperformed on a certain area from the front edge side of the OPC area301.

The size of the area may be determined in advance, and it is set not toexceed the rear edge of the recording area. Moreover, in the example,the recording of the calibration data is performed from the low powerside, and the power increases sequentially and gradually as therecording proceeds to the rear edge side. Incidentally, in thecalibration area 303 (or a judgment area) in FIG. 5, the recorded datais shown by a monotone drawing which becomes relatively dark as therecording is performed with a relatively high power.

If the recording of the calibration data is ended, then, as shown in themiddle part of FIG. 5, the judgment data is recorded into the unusedarea which is adjacent to the front edge side of the calibration area303, with a power that is lower than the power when the recording of thecalibration data is ended and that allows the recorded area to bedetected by the information reproducing device 108. The recording of thejudgment data is performed from the front edge side of the OPC area 301to the rear edge side in order not to overlap the calibration area 303.At this time, there may be a space left in which the data is notrecorded between the calibration area 303 and the judgment area 304. Thecalibration area 303 generated by the recording and a judgment area 304a in which the judgment data is recorded are collectively referred to asa unit OPC area 302 a. Incidentally, the unit OPC area 302 a indicates,in effect, an area in which the calibration data is recorded by one OPC.The aforementioned OPC area 301 preferably has a size large enough to beprovided with a plurality of unit OPC areas 302 a therein.

Moreover, in the recording of the judgment data, it is only necessary tosatisfy such conditions that the power is lower than the power when therecording of the calibration data is ended and that the power allows therecorded area to be detected by the information reproducing device 108.For example, as shown in the lower part of FIG. 5, not only therecording with the same power but also the recording with the recordingpower changed may be performed. At this time, in the example, therecording is performed from the high power side, and the power decreasessequentially and gradually as the recording proceeds to the rear edgeside. The judgment area 304 b is one example of the above situation, andthe recording is performed with a power that is lower than the powerwhen the recording of the calibration data is ended and with the powerreduced sequentially.

As described above, in recording the calibration data, the unused areais sought from the front edge of the OPC area 301 to the rear edge.Here, if the calibration data is recorded multiple times on one opticaldisc 100, then, the next calibration data is recorded on the front edgeside of the firstly detected judgment area 304 a because the judgmentarea 304 a always exists on the rearmost edge of the unrecorded area onthe OPC area 301.

According to the operations, it is possible to make the judgment areas304 a and 304 b for judging that the calibration data is recorded, inthe area adjacent to the calibration area 303, which facilitates thedetection of the area in which the calibration data has not beenrecorded. In particular, if the calibration data is recorded in order toincrease the power sequentially, it is likely hard to distinguishbetween the generated calibration area 303 and the unused area adjacentto the calibration area 303 because the calibration data is recordedwith the lowest power at the beginning. Thus, it is possible to clearlyidentify the edge of the area in which the calibration data is recorded,by performing the recording to be adjacent to the area in which thecalibration data is recorded at the beginning, with the power that isless than or equal to the power immediately before the recording of thecalibration data is ended (i.e. the highest power). This effect isremarkable when the OPC process is performed multiple times.

The present invention is not limited to the aforementioned examples, butvarious changes may be made, if desired, without departing from theessence or spirit of the invention which can be read from the claims andthe entire specification. An information recording medium, aninformation recording apparatus and method, and a computer program forrecording control, all of which involve such changes, are also intendedto be within the technical scope of the present invention.

1. An information recording apparatus comprising: a recording device forrecording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling device for controlling therecording device to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting device for detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling device; an ending device for endingthe irradiation of the recording laser beam by the control of thecontrolling device in a case where the degree of modulation detected bythe detecting device exceeds a predetermined range; and a determiningdevice for determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending device, wherein the case where thedegree of modulation detected by the detecting device exceeds thepredetermined range is a case where a push-pull signal estimated fromthe degree of modulation detected by the detecting device exceeds areading limit level of the push-pull signal.
 2. The informationrecording apparatus according to claim 1, wherein the informationrecording medium allows reflectance to be increased when the informationis recorded.
 3. The information recording apparatus according to claim1, wherein the controlling device controls the recording device torecord the calibration data by using the recording laser beam with onepower and then record the calibration data by using the recording laserbeam with another power, which is greater than or equal to the onepower, when the power is adjusted gradually.
 4. The informationrecording apparatus according to claim 3, wherein the controlling deviceends the recording of the calibration data and then irradiates again anarea on the information recording medium that is adjacent to an area inwhich the calibration data is recorded, with a power that is less thanor equal to a power immediately before the recording of the calibrationdata is ended.
 5. The information recording apparatus according to claim1, further comprising: a judging device for judging whether or notrecording quality of the information recorded by using the recordinglaser beam with the optimum power determined by the determining deviceis at an acceptable level; and a modifying device for adjusting arecording pulse of the recording laser beam upon it being judged thatthe recording quality is not at the acceptable level.
 6. The informationrecording apparatus according to claim 5, wherein the controlling devicecontrols the recording device to record the calibration data again afterthe adjustment of the recording pulse of the recording laser beam on themodifying device.
 7. The information recording apparatus according toclaim 1, wherein the detecting device detects a difference between thedegree of modulation in each power of the gradually adjusted recordingpower and the degree of modulation in a previous recording power of thegradually adjusted recording power when detecting the degree ofmodulation.
 8. An information recording method comprising: a recordingprocess of recording information onto an information recording medium byirradiating the information recording medium with a recording laser beamwhose power can be adjusted; a controlling process of controlling therecording process to record calibration data by irradiating theinformation recording medium with the recording laser beam in which thepower is adjusted gradually; a detecting process of detecting degree ofmodulation in an area in which the calibration data is recorded on theinformation recording medium every time the power is adjusted graduallyby the control of the controlling process; an ending process of endingthe irradiation of the recording laser beam by the control of thecontrolling process in a case where the degree of modulation detected bythe detecting process exceeds a predetermined range; and a determiningprocess of determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending process, wherein the case where thedegree of modulation detected by the detecting process exceeds thepredetermined range is a case where a push-pull signal estimated fromthe degree of modulation detected by the detecting process exceeds areading limit level of the push-pull signal.
 9. A non-transitorycomputer-readable medium with a computer program recorded thereon fortangibly embodying a program of instructions executable by a computerfor making the computer function as: a recording device for recordinginformation onto an information recording medium by irradiating theinformation recording medium with a recording laser beam whose power canbe adjusted; a controlling device for controlling the recording deviceto record calibration data by irradiating the information recordingmedium with the recording laser beam in which the power is adjustedgradually; a detecting device for detecting degree of modulation in anarea in which the calibration data is recorded on the informationrecording medium every time the power is adjusted gradually by thecontrol of the controlling process; an ending device for ending theirradiation of the recording laser beam by the control of thecontrolling device in a case where the degree of modulation detected bythe detecting device exceeds a predetermined range; and a determiningdevice for determining an optimum power for recording the information,on the basis of a reproduction signal obtained by reading thecalibration data after the irradiation of the recording laser beam isended by the control of the ending device, wherein the case where thedegree of modulation detected by the detecting device exceeds thepredetermined range is a case where a push-pull signal estimated fromthe degree of modulation detected by the detecting device exceeds areading limit level of the push-pull signal.